Abstract: As a non-essential, highly toxic heavy metal element, thallium (Tl) interferes with normal development of plants and causes serious toxicity accumulation in food chain. Root secretion of organic acids plays an important role in the resistance against heavy metal pollution. In order to study the relationship between heavy metal absorption and organic acid tolerance mechanisms under Tl stress, the oxalate secretion and Tl distribution under T1 stress were studied by hydroponic method. Oxalate content and Tl absorption and distribution in rice (Oryza sativa L.) were analyzed. With the increase of Tl concentration from 10 to 25 μmol·L^-1, the content of oxalate secreted in rice rhizosphere was increased gradually; however, the amount of oxalate secretion was gradually decreased with the prolongation of Tl stress time. Anion channel inhibitors phenylglyoxal (PG) and niflumic acid (NIF) significantly inhibited the excretion of oxalate in roots, and the inhibition of NIF was stronger than that of PG. The roots of rice could accumulate more Tl than leaves, and root cytoplasm was the main location of Tl storage. There was a significant positive correlation between oxalate content in root and Tl content in plant (r=0.923, P<0.01). It was suggested that oxalate in rice roots played an important role in the tolerance to Tl in rice plants.

Key words: thallium(Tl), oxalate, anion channel inhibitor, uptake and distribution, rice (Oryza sativa L.)

摘要： 铊（Tl）作为一种非必需、高毒性重金属元素，会干扰植物的正常发育，并在食物链中引起严重的毒性积累。根系分泌有机酸在抗重金属污染中起着重要作用。为研究铊胁迫下的植物根系有机酸分泌特征与重金属吸收的关系，利用水培法对Tl胁迫下水稻（Oryza sativa L.）植株草酸分泌和Tl分布特征进行检测和分析，研究不同抑制剂对水稻草酸含量及Tl含量的影响，并分析水稻内部草酸含量与Tl吸收及分布的相关性。结果显示，Tl胁迫浓度从10 μmol·L^-1提高到25 μmol·L^-1，水稻根系外分泌的草酸量呈上升趋势；但随着铊胁迫时间的延长，草酸分泌量又逐渐减少。阴离子通道抑制剂苯基乙二醛（PG）和尼氟酸（NIF）显著抑制根系外泌草酸含量，NIF的抑制作用强于PG。根比叶积累更多的Tl，其中根细胞质是储存Tl的主要部位。水稻根系内草酸含量与植株Tl含量呈极显著正相关（r=0.923，P<0.01)，表明水稻根系内部草酸含量对水稻植株耐受Tl具有重要作用。

关键词: 铊, 草酸, 阴离子通道抑制剂, 吸收和分配, 水稻（Oryza sativa L.）